1. Field of the Invention
Aspects of the present invention relate to an optical unit, an image forming apparatus including the same and an optical element thereof, and, more particularly, to an optical unit whose optical element can be more accurately mounted thereon by a curing adhesive, an image forming apparatus including the optical unit, and an optical element of the optical unit.
2. Description of the Related Art
An electrophotographic type image forming apparatus performs a series of processes including charging, exposing, developing, transferring and fusing to form an image onto a printable medium. Examples of an electrophotographic type image forming apparatus include a laser printer, a multi-function printer, a facsimile machine, and a copying machine. The image forming apparatus has an optical unit to perform the exposing process. Such an optical unit includes an f-θ lens to focus light scanned by a light source onto a predetermined photosensitive medium.
The f-θ lens is installed in the optical unit using an ultraviolet-curing adhesive. However, as the ultraviolet-curing adhesive contracts when cured, the f-θ lens, which was located at an ideal position before the ultraviolet-curing adhesive contracts, shifts to a position deviated from the original position after the ultraviolet-curing adhesive has contracted.
To enhance such phenomenon, a Japanese patent publication No. 2004-151388 discloses a method where a part of the ultraviolet-curing adhesive is cured prior to another part.
FIG. 1 is a schematic view describing a manufacturing method of a conventional optical unit. As shown in FIG. 1, an f-θ lens 11 is precisely disposed at a predetermined position on a mount member 12 during the design process. To this end, the present position of the f-θ lens 11 is precisely measured using a sensor. The position of the f-θ lens 11 is corrected properly based on the measurement of the sensor. The ultraviolet-curing adhesive 13 is inserted between the mount member 12 and the f-θ lens 11.
First, only a center part 13c of the adhesive 13 is cured by an ultraviolet ray L, using a mask 22 having an opening 22a. Accordingly, deformation of the adhesive 13 is small as compared to curing the whole adhesive 13. The ultraviolet ray L is scanned by an ultraviolet ray scanning device 21b. 
After curing the center part 13c, the mask 22 is removed to cure a surrounding part 13d. Accordingly, as a remaining part of the adhesive 13 is cured while the position of the f-θ lens 11 has been fixed by curing the center part 13c first, displacement of the f-θ lens 11 due to the contraction of the adhesive 13 can be minimized.
However, the mask 22 is required to mount the f-θ lens 11. Therefore, if the part where the adhesive is to be bonded is changed, the shape of the mask should also be changed, thus incurring costs for manufacturing, managing and maintaining the additional masks. Also, in a manufacturing process of the conventional optical unit, processes for disposing the mask 22 at a proper position and removing the mask 22 are required. Accordingly, overall manufacturing cost of the optical unit is increased.